French Patent No. 2,221,409 discloses a glass sheet forming apparatus for sag bending a heated glass sheet. Therein, the apparatus has interposed upper and lower horizontal parallel rollers. The upper rollers are arranged in two staggered rows, one extending from each side of the apparatus beyond a center line of the apparatus for receiving and conveying a heated glass sheet. The upper rollers are free about one end and pivotal about a fixed pivot point at the other end and work in conjunction with the lower horizontal rollers. A heated glass sheet received on the upper rollers is sag bent by pitching the upper rollers downwardly relative to the lower horizontal rollers whereby the glass sheet is sag bent to a desired shape.
Forming a glass sheet with such an apparatus marks the glass sheet as it sags along the upper rolls as the rolls are pitched downwardly. Furthermore, the fixed pivot points of the ends of the upper rollers limit the shapes that can be formed in the heated glass sheet.
In my earlier U.S. Pat. No. 4,586,946, I overcame the problems associated with sag bending with such an apparatus by disclosing a glass sheet bending apparatus including a main conveyor having straight rollers at a fixed upper elevation. I interposed stationary downwardly curved forming bars between the straight rollers at a second lower elevation. A pressing means mounted above the first elevation is actuated downwardly as the straight rollers are lowered to bend a heated glass sheet against the curved lower forming bars.
This apparatus which requires vertical movement of the main conveyor and pressing means was designed for symmetrically bending glass sheets. Such an apparatus is unable to bend heated glass sheets to a non-symmetrically curved bent shape because the roll technology as disclosed in U.S. Pat. Nos. 3,545,951; 4,226,608; and 4,311,509 would not allow a portion of the roll to have a dissimilar curvature than another portion of the same roll.